Lesson 2 of 11 · 6 min
The human endocrine system and hypothalamus
NCERT §19.2 and §19.2.1
Meher's biology teacher asks the class to point at every endocrine gland on their own bodies. Most students stop at the neck. Where else should they point, and which gland commands the others?
The lesson in notes
In short
The endocrine system is made up of the endocrine glands together with hormone-producing diffuse tissues and cells found in different parts of the body.
The organised endocrine bodies are eight: pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and the gonads (testes in a male, ovaries in a female). Some other organs, such as the gastrointestinal tract, liver, kidney and heart, also make hormones.
The hypothalamus is the basal part of the diencephalon of the forebrain and regulates a wide range of body functions.
It contains several groups of neurosecretory cells, called nuclei, that make hormones. These hormones control the synthesis and secretion of pituitary hormones.
Hypothalamic hormones are of two kinds: releasing hormones, which stimulate pituitary secretion, and inhibiting hormones, which inhibit it.
Examples: gonadotrophin releasing hormone (GnRH) stimulates the pituitary to make and release gonadotrophins; hypothalamic somatostatin holds back the pituitary's release of growth hormone (GH).
These hormones are made in hypothalamic neurons, travel down their axons and are released at the nerve endings. They reach the pituitary through a portal circulatory system and regulate the anterior pituitary.
The posterior pituitary, by contrast, is under direct neural regulation by the hypothalamus.